Driven by the increasing price of gasoline as well as the requirements for carbon dioxide reduction, the automotive industry is active in developing new technologies to improve vehicle fuel economy. One solution under development by many players in the industry is using lightweight materials to reduce vehicle weight.
Among the lightweight materials, carbon fiber is a well-known low-density material with good mechanical properties. Carbon fiber has been used in aerospace, wind energy, sporting goods and high-end vehicles. In these areas, the use of carbon fibers is in general of relatively lower volume but with a higher price tag compared with automotive industry. It may thus to be desirable to implement carbon fibers to high volume non-luxury vehicles in automotive industry.
One of the challenges resides in developing low cost processing technology for high volume production of carbon fibers. Sheet molding compound (SMC) process has been successfully used to manufacture glass fiber reinforced parts such as deck-lids, hoods and bumpers. However, it is not straightforward to use the same process for carbon fibers due to differences in physical properties. Carbon fibers are significantly smaller in diameter than glass fibers. This makes carbon fibers difficult to separate. In addition, the sizing materials coated on the carbon fiber surface make carbon fibers tend to agglomerate.
The bundling of carbon fibers causes is problematic in the SMC process, with one being that it becomes difficult for resin to wet out, and the other being that fibers do not flow well during molding. Carbon fiber reinforced SMC parts have not met the required mechanical performance due to one or more of these problems. An economical and effective method needs to be developed to improve the carbon fiber separation in carbon fiber SMC process in order to improve final part performance.
It would thus be advantageous if SMC such as carbon fiber reinforced SMC may be produced without these identified problems, particularly problems in relation to difficulties in carbon fiber de-bundling and filament separation.